The fibroblast growth factor (FGF) group of cytokines includes at least 21 members that regulate diverse cellular functions such as growth, survival, apoptosis, motility and differentiation. The FGF family of proteins, whose prototypic members include acidic FGF (FGF-1) and basic FGF (FGF-2), bind to four related receptor tyrosine kinases. These molecules transduce signals via high affinity interactions with cell surface tyrosine kinase FGF receptors (FGFRs). These FGF receptors are expressed on most types of cells in tissue culture. Dimerization of FGF receptor monomers upon ligand binding has been reported to be a requisite for activation of the kinase domains, leading to receptor trans phosphorylation. FGF receptor-1 (FGFR-1), which shows the broadest expression pattern of the four FGF receptors, contains at least seven tyrosine phosphorylation sites. A number of signal transduction molecules are affected by binding with different affinities to these phosphorylation sites.
In addition to participating in normal growth and development, known FGFs have also been implicated in the generation of pathological states, including cancer. FGFs may contribute to malignancy by directly enhancing the growth of tumor cells. For example, autocrine growth stimulation through the co-expression of FGF and FGFR in the same cell has been reported to lead to cellular transformation.